A lubricant may be a liquid, a paste, or a solid with liquid lubricants being the most used. Lubricating oils may be used in automobile engines, transmissions, bearings, gears, industrial gears and other machinery to reduce friction and wear and to increase fuel economy. A number of components including, but not limited to dispersants, detergents, friction modifiers, antiwear agents, antioxidants, and anti-corrosion additives are typically present in fully formulated lubricating oils. For many lubricant applications, a viscosity index improver may also be included as a major component.
With the energy resources depleting and more stringent environmental regulations being adopted, there exists a greater demand to increase a fuel economy of vehicles and to decrease emissions in vehicle exhausts. Currently, organic friction modifiers are added to the lubricating oils to increase fuel economy. However, the level of the fuel economy achievable by organic friction modifiers is limited. Hence, there is a need for alternate methods for achieving improvements in fuel economy.
One method for increasing fuel economy is to provide lower viscosity grade lubricating oils. While providing lower viscosity lubricating oils may dramatically increase fuel economy, such lubricating oils may also increase wear. Wear may be partially reduced by using antiwear agents such as zinc dialkyldithiolphosphate (ZDTP). However, ZDDP contains phosphorus and its decomposition products may have deleterious effects on automotive catalyst systems for emission control. Accordingly, there remains an increasing need for methods for reducing friction and wear without adversely affecting emission control systems and without further depleting scarce natural resources.
With regard to the above, exemplary embodiments described herein provide methods for reducing friction coefficients and wear between lubricated surfaces. The method includes providing an amount of metal-containing nanoparticles dispersed in a fully formulated lubricant composition containing a base oil of lubricating viscosity. The nanoparticles have a formula of (Aa)m(Bb)nXx, wherein each of A, B is selected from a metal, X is selected from the group consisting of oxygen and sulfur, subscripts a, b, and x represent compositional stoichiometry, and each of m and n is greater than or equal to zero with the proviso that at least one of m and n is greater than zero, wherein the nanoparticles have an average particles size ranging from about 1 to about 10 nanometers. The lubricant composition containing the metal-containing nanoparticles is applied to a surface to be lubricated.
In another embodiment, there is provided a method of reducing a friction coefficient of an engine lubricant composition during operation of an engine containing the lubricant composition. The method includes contacting the engine parts with a fully formulated lubricant composition that contains a base oil of lubricating viscosity and an amount of metal-containing nanoparticles sufficient to reduce the friction coefficient to below a friction coefficient of a lubricant composition devoid of the metal-containing nanoparticles. The nanoparticles have a formula of (Aa)m(Bb)nXx, wherein each of A, B is selected from a metal, X is selected from the group consisting of oxygen and sulfur, subscripts a, b, and x represent compositional stoichiometry, and each of m and n is greater than or equal to zero with the proviso that at least one of m and n is greater than zero. The nanoparticles in the lubricant composition have an average particle size ranging from about 1 to about 10 nanometers.
A further embodiment of the disclosure provides a method for reducing wear between moving parts using a lubricating oil. The method includes using as the lubricating oil for one or more moving parts a lubricant composition containing a base oil, and an oil additive package including a wear reducing agent. The wear reducing agent is made of dispersed metal-containing nanoparticles, wherein the amount of nanoparticles in the lubricant composition ranges up to about 5 percent by weight of the total lubricant composition. The metal-containing nanoparticles have a formula of (Aa)m(Bb)nXx, wherein each of A, B is selected from a metal, X is selected from the group consisting of oxygen and sulfur, subscripts a, b, and x represent compositional stoichiometry, and each of m and n is greater than or equal to zero with the proviso that at least one of m and n is greater than zero.
Another embodiment of the disclosure provides a lubricant composition containing a base oil of lubricating viscosity and a boundary friction reducing amount of metal-containing nanoparticles dspersed in the base oil. The metal-containing nanoparticles have a formula of (Aa)m(Bb)nXx, wherein each of A, B is selected from a metal, X is selected from the group consisting of oxygen and sulfur, subscripts a, b, and x represent compositional stoichiometry, and each of m and n is greater than or equal to zero with the proviso that at least one of m and n is greater than zero. The nanoparticles have an average particles size ranging from about 1 to about 10 nanometers, and are effective to reduce a boundary friction coefficient between lubricated metal surfaces to below a boundary friction coefficient between the lubricated metal surfaces of a lubricant composition devoid of the metal-containing nanoparticles.
Yet another embodiment of the disclosure provides oil dispersible cerium oxide nanoparticles derived from a cerium acetate solution of amine and organic acid. The cerium acetate solution is irradiated by a high frequency electromagnetic radiation source to provide oil dispersible nanoparticles having a substantially uniform particle size ranging from about 1 to about 10 nanometers.
As set forth briefly above, embodiments of the disclosure provide unique finished lubricant compositions that may significantly improve the coefficient of friction of the lubricant composition and may reduce wear for relatively low viscosity lubricant compositions. An additive package containing the metal-containing nanoparticales may be mixed with an oleaginous fluid that is applied to a surface between moving parts. In other applications, an additive package containing the metal-containing nanoparticles may be provided in a fully formulated lubricant composition.
The methods and compositions described herein may also be suitable for reducing emissions of CO and hydrocarbons (HC) from engines lubricated with the lubricant compositions described herein. It is well known that certain metals may be useful for improving the burning efficiency of fuels. For example, metal-containing nanoparticles from the lubricants may enter the combustion chamber by leaking around the piston rings thereby providing a catalytic source suitable for improving fuel combustion without directly adding metal compounds to the fuel. Other features and advantages of the methods described herein may be evident by reference to the following detailed description which is intended to exemplify aspects of the exemplary embodiments without intending to limit the embodiments described herein.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the embodiments disclosed and claimed. The phrases “having the formula” or “have the formula” are intended to be non-limiting with respect to nanoparticles or nanoalloy particles described herein. The formula is given for the purposes of simplification and is intended to represent mono-, di-, tri-, tetra-, and polymetallic nanoparticles.